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33%? ALBEBT BOECK, GE WORCESTER, MASSACHUSETTS, ASSIGNOR TO NORTONCOMPANY, OF WORCESTER, MASS&CHUSETTE, A GOEPORA'IION 0F MASSACHU-Patented Dec. T6, 191$.

SETTS.

.EOBOUS 311 iCLE.

1,8ll,573. Specification of Letters Patent.

an} Drawing.

Application filedmay 29, 1912. fierial No. 700,398.

T 0 all whom it may concern Be it known that T, Pia-nor A. Boron, a

'citizen of the United States, residing at l i orcester, in the countyof Worcester and State of Massachusetts, have invented certain new anduseful Improvements in Porous Articles, of which the following is aspecification.

This invention relates to thin-walled porous articles consistingessentially of previously molten alumina, or of other highly refractorymaterial such as corundum or carborundum, in conjunction with a ceramicbond, in proper proportions to yield an article which is permeable toliquids and gases, and hence adapted for use as filters, electrolyticdiaphragms, and for other purposes. For example, articles in accordancewith this invention may be made as follows: Calcined bauxite or otherimpure commercial form of alumina, or pure or purified alumina preparedby chemical methods, is fused in an electric furnace, and'the product iscrushed to grain and graded, in the known manner as practiced for themanufacture of abrasive articles. This product is hereinafter referredto as alumina grain. The grains are preferably then roasted in anoxidizing atmosphere in order to eliminate traces of carbids or.otherreduction products, which if present in the finished article, mightcause local disintegration or pitting of the body. The grain is thenmixed with a smallproportion, usually from five to fifteen per cent, orsomewhat more, of a plastic clay, which serves as a bond, and sufficientwater to produce a thin slip or body of suitable consistency to form thearticle. paratively thin layer to the surface of a suitable mold orform, which should be highly absorptive in character. Plaster of Parisis suitable for the preparation of such molds or forms. The mold withthe applied refractory coating is then dried at moderate temperatures,say about 50 0., after which the article may be separated from the moldand will be found sufiiciently strong to endure firing. The molds orforms may be used an indefinite number of times. The firing isaccomplished in kilns under standard conditions and at temperaturesSlllllciently high to fuse, vitrify or in some in- The slip is thenapplied as a comstances to partially vitrify the bond, as may berequired by porositypr other characteristics desired in the body.

By the use of small proportions of a clay or other ceramic bond, asabove described, a double result is secured; for the articles may bemade highly porous, possessing a remarkably high filtering capacity perunit area; and they retain in a large measure the refractory characterand chemical inertness of the alumina grain.

Crucibles made as above described may replace the so-called Goochcrucibles for analytical purposes; and are also adapted formelting'metals and other materials on a laboratory or on a technicalscale. They have a thermal conductivity more than one and a half timesthat of the best porcelain, this being of great advantage in connectionwith all heat processes.

Among the many articles which may be advantageously made in accordancewith this invention may be mentioned extraction thimbles or vessels foruse with volatile solvents; filtering tubes, cylinders or disks forportable waters; porous diaphragms in the form of sheets, cups orvessels for electrolytic purposes; and the like. Such articles may beporous over their entire surface, or portions thereof may be glazed, asfor example the marginal portions of the crucibles and extractionthimbles, the ends of the tubes or cylinders, etc.

The degree of porosity of the articles may be varied within certainlimits by varying the proportion of the clay bond, thehighest porosityas well as the most refractory article being secured by using theminimum proportion of a highly plastic clay. The porosity may also becontrolled within certain limits by varying the size of the grain. Whenalumina is used, grains between 46 and 220 mesh have been found bestsuited for general purposes.

It will be noted that the materials referred to as suitable for use inthe manufacture of articles of the kind above referred to, are all suchas have in the course of their production, been subjected to veryhigh'temperatures, of the degree available only in electric furnaces,and the term highly refractory is intended to characterize suchmaterials.

I claim: conjunction with a small proportion of a 1. A thin-walledporous article adapted ceramic bond. 1 for use as a filter andconsisting essentially In testimony whereof, I aflix my signature ofalumina grain in conjunction with a in presence of two Witnesses.

small proportion of a ceramic bond. PERCY ALBERT BOECK,

2. A thin-walled porous article adapted Witnesses: for use as a filterand consisting essentially CHAS. R. MILLER, of grains ofwhighly-refractory material in H. O. ANDERSON.

